1. Field of the Invention
The present invention relates to a measuring instrument and a method of measuring by using the measuring instrument for measuring a size of an affected part of an organ in a body, vessel, vas and celom such as aneurysm, artery and vein malformation, tumor or the like by using an X-ray photographing device, and particularly relates to a measuring instrument and a measuring method using the measuring instrument for measuring an actual size of an affected part in a brain.
2. Description of the Related Art
It is important in the field of brain surgery to measure a size, such as a diameter, of a brain artery aneurysm, a diameter of a vessel, a size of a brain artery and vein malformation (AVM) or the like in considering selection of an optimum coil size in a brain artery aneurysm plugging operation, an amount of a plugging drug to be used, adaptation of a .gamma. knife with respect to AVM and the like. Conventionally, in the heart vessel imaging field, a catheter, a guide wire or the like is inserted into a vicinity of an affected part and X-ray imaging is performed to calculate a diameter of a vessel from a proportion of the size of the instrument to the diameter of the vessel. However, when a danger of laceration is conceivable as, for example, in brain aneurysm, a catheter having a large diameter cannot be advanced to an affected part.
In such a case, there has been used a method in which a metal ball or the like is placed outside of a body as an index and a size of an affected part is approximately calculated from a proportion of the diameter of the metal ball to the size of the affected part.
However, when the index placed outside of a body and the affected part present inside of the body are made to be simply proportional to each other, since X-rays diverged radially, the magnifications of the index and the affected part in the X-ray vessel photographing, are changed in accordance with a distance between an X-ray tube (light source) and an imaging intensifier (I.I.) (light receiving portion) and positions of the index and the affected part and therefore, there causes an error between a calculation result and an actual size depending on the position (depth) of the affected part. Thus, this method is devoid of accuracy.